共查询到20条相似文献,搜索用时 31 毫秒
1.
Steels containing about 12 pct Cr, 10 pct Mn, and 0.2 pct N have been shown to have an unstable austenitic microstructure
and have good ductility, extreme work hardening, high fracture strength, excellent toughness, good wear resistance, and moderate
corrosion resistance. A series of alloys containing 9.5 to 12.8 pct Cr, 5.0 to 10.4 pct Mn, 0.16 to 0.32 pct N, 0.05 pct C,
and residual elements typical of stainless steels was investigated by microstructural examination and mechanical, abrasion,
and corrosion testing. Microstructures ranged from martensite to unstable austenite. The unstable austenitic steels transformed
to α martensite on deformation and displayed very high work hardening, exceeding that of Hadfield’s manganese steels. Fracture
strengths similar to high carbon martensitic stainless steels were obtained while ductility and toughness values were high,
similar to austenitic stainless steels. Resistance to abrasive wear exceeded that of commercial abrasion resistant steels
and other stainless steels. Corrosion resistance was similar to that of other 12 pct Cr steels. Properties were not much affected
by minor compositional variations or rolled-in nitrogen porosity. In 12 pct Cr-10 pct Mn alloys, ingot porosity was avoided
when nitrogen levels were below 0.19 pet, and austenitic microstructures were obtained when nitrogen levels exceeded 0.14
pct. 相似文献
2.
Younghwan Jang Sangshik Kim Jehyun Lee 《Metallurgical and Materials Transactions A》2005,36(5):1229-1236
The tensile and corrosion behaviors of CD4MCU cast duplex stainless steels with different Mo contents of 0, 2, and 4 pct,
respectively, were examined in the present study. The polarization and the in-situ slow-strain-rate (SSR) tests were conducted in a 3.5 pct NaCl+5 pct H2SO4 aqueous solution to quantify the resistances to pitting corrosion and stress corrosion cracking (SCC) with different Mo contents.
The addition of Mo, which is a strong ferrite stabilizer, affected the microstructure of the present alloy and, eventually,
the tensile and corrosion behaviors in a complex manner. The tensile properties of CD4MCU cast duplex stainless steel, for
example, were found to be determined by the volume fraction of hard ferritic phase, the presence of the second precipitates
of soft austenitic phase in the ferrite matrix, and the shape of the austenitic phase. The addition of 2 pct Mo was detrimental
to the corrosion properties of CD4MCU cast duplex stainless steel due to the significant increase in the volume fraction of
ferritic phase. With the addition of 4 pct Mo, however, the resistances to pitting corrosion and SCC recovered to those of
the specimen without Mo. The relationship between the microstructural evolution and the tensile and corrosion behavior of
CD4MCU cast duplex stainless steels with different Mo contents was discussed based on the micrographic and fractographic observations. 相似文献
3.
Jinil Son Sangshik Kim Jehyun Lee Byunghak Choi 《Metallurgical and Materials Transactions A》2003,34(8):1617-1625
The effect of N addition on the microstructure, tensile, and corrosion behaviors of CD4MCU (Fe-25Cr-5Ni-2.8Cu-2Mo) cast duplex
stainless steel was examined in the present study. The slow strain rate tests were also conducted at a nominal strain rate
of 1 × 10−6/s in air and 3.5 pct NaCl+5 pct H2SO4 solution for studying the stress corrosion cracking (SCC) behavior. It was observed that the volume fraction of austenitic
phase in CD4MCU alloy varied from 38 to 59 pct with increasing nitrogen content from 0 to 0.27 wt. pct. The tensile behavior
of CD4MCU cast duplex stainless steels, which tended to vary significantly with different N contents, appeared to be strongly
related to the volume changes in ferritic and austenitic phases, rather than the intrinsic N effect. The improvement in the
resistance to general corrosion in 3.5 pct NaCl+5 pct H2SO4 aqueous solution was notable with 0.13 pct N addition. The further improvement was not significant with further N addition.
The resistance to SCC of CD4MCU cast duplex stainless steels in 3.5 pct NaCl+5 pct H2SO4 aqueous solution, however, increased continuously with increasing N content. The enhancement in the SCC resistance was believed
to be related to the volume fraction of globular austenitic colonies, which tended to act as barriers for the development
of initial pitting cracks in the ferritic phase into the sharp ones. 相似文献
4.
D. G. Kolman J. F. Bingert R. D. Field 《Metallurgical and Materials Transactions A》2004,35(11):3445-3454
The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order
to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3,
6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having
a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less
than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility.
Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis
indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue
crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation
and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement
is partially responsible for increased embrittlement. 相似文献
5.
Deformation dilatometry is used to simulate the hot rolling of 0.20 pct C-1.10 pct Mn steels over a product thickness range
of 6 to 170 mm. In addition to a base steel, steels with additions of 0.02 pct Ti, 0.06 pct V, or 0.02 pct Nb are included
in the study. The transformation behavior of each steel is explored for three different austenite grain sizes, nominally 30,
55, and 100 μm. In general, the volume fraction of Widmanst?tten ferrite increases in all four steels with increasing austenite
grain size and cooling rate, with austenite grain size having the more significant effect. The Nb steel has the lowest transformation
temperature range and the greatest propensity for Widmanst?tten ferrite formation, while the amount of Widmanst?tten ferrite
is minimized in the Ti steel (as a result of intragranular nucleation of polygonal ferrite on coarse TiN particles). The data
emphasize the importance of a refined austenite grain size in minimizing the formation of a coarse Widmanst?tten structure.
With a sufficiently fine prior austenite grain size (e.g., ≤30 μm), significant amounts of Widmanst?tten structure can be avoided, even in a Nb-alloyed steel. 相似文献
6.
Younghwan Jang Jinil Son Sanghik Kim Jehyun Lee Byunghak Choi 《Metallurgical and Materials Transactions A》2004,35(11):3431-3438
The tensile and corrosion behaviors of 0.13 pct N-containing CD4MCU cast duplex stainless steels with different Cr contents
ranging from 23 to 28 pct were examined in the present study. The polarization tests were conducted in 3.5 pct NaCl + 5 pct
H2SO4 aqueous solution for general corrosion resistance, and the in-situ slow strain rate (SSR) tests were also conducted in air and 3.5 pct NaCl + 5 pct H2SO4 aqueous solution to quantify the resistance to stress corrosion cracking (SCC) of the three materials. A substantial microstructural
change in 0.13 pct N-containing CD4MCU cast duplex stainless steel was observed with different Cr contents, which in turn
affected the tensile and corrosion behaviors significantly. Tensile behavior of 0.13 pct N-containing CD4MCU cast duplex stainless
steel, for example, varied in a nonlinear manner with different Cr contents due to the volume change of hard ferritic phase
and the presence of the second precipitates of soft austenitic phase in the ferrite matrix. The beneficial effect of Cr for
improving the general corrosion and the SCC resistances was largely overshadowed by this variation in microstructural characteristics.
The relationship between the microstructural evolution and the tensile and corrosion behavior of 0.13 pct N-containing CD4MCU
cast duplex stainless steels with different Cr contents was discussed based on the optical microscopy and scanning electron
microscopy (SEM) micrographic and fractographic observations. 相似文献
7.
The formation of austenite from different microstructural conditions has been studied in a series of 1.5 pct Mn steels that
had been heated in and above the intercritical (α+ γ) region of the phase diagram. The influence of variables such as cementite morphology, initial structural state of the ferrite
and the carbon content has been assessed in terms of their respective effects on the kinetics of austenite formation and final
microstructure. Austenite was found to form preferentially on ferrite-ferrite grain boundaries for all initial structures.
The results of this study have shown that the 1.5 pct Mn has lowered both the AC3 and AC1, lines causing large amounts of austenite to form in low carbon steel. The kinetics of austenite formation at 725 °C were
not only very slow but also were approximately independent of the amount formed. Austenite appeared to form slightly more
rapidly from cold rolled ferrite than from recrystallized ferrite or ferrite-pearlite structures. 相似文献
8.
J. M. Vitek A. Dasgupta S. A. David 《Metallurgical and Materials Transactions A》1983,14(9):1833-1841
The microstructural modifications in three austenitic stainless steels (types 308, 310, and 312) were evaluated after rapid
solidification. These three steels are commonly used weld filler metals. Two methods of rapid solidification were investigated,
autogenous laser welding and arc-hammer splat quenching. The structure of 310 stainless steel was found to be 100 pct austenite,
and did not vary over the range of conditions studied. On the contrary, the structures of types 308 and 312 steels were very
sensitive to the cooling rates and solidification conditions. With the highest cooling rates, the type 308 structure was fully
austenitic while the type 312 structure was fully ferritic. At lower cooling rates, the structures were duplex ferrite plus
austenite. The results were interpreted in terms of faster kinetics of solidification of austenite compared to ferrite under
the conditions examined. A comparison of the structures produced by the two rapid solidification techniques indicated the
cooling rates are comparable. 相似文献
9.
The effect of solution annealing temperature ranging from 950 to 1 200℃ on the microstructure and corrosion performance of duplex stainless steel(DSS)2204 were investigated.The proportion of the ferrite phase increased while the austenite phase decreased and the ferrite stabilizing elements diluted in the ferrite phase with the increase of annealing temperature.The critical pitting temperature(CPT)of specimens annealed at 1 000℃ was higher than those annealed at 950 ℃,whereas further increasing the annealing temperature to 1 200 ℃ decreased the CPT.The pitting initiation sites were observed in the austenite phase,at the boundary of ferrite/austenite phase and inside the ferrite phase for specimens annealed at 950,1 000℃ and exceeding 1 100℃,respectively.The evolution trend of the CPT and the pit initiation site were analyzed by the pitting resistance equivalent number. 相似文献
10.
11.
含氮双相不锈钢及其冶金工艺 总被引:4,自引:0,他引:4
铁素体-奥氏体双相不锈钢比奥氏体不锈钢有较高的机械性能、优良的耐应力腐蚀和点腐蚀性能以及较低的价格(Ni含量低),特别是通过降低钢中的碳含量和增加氮含量而改善了钢的可焊性。双相钢中含较高的氮含量有两个有利的因素:抑制δ-铁素体的形成和提高抗点蚀当量。介绍了4种不同类型的含氮双相不锈钢和常用双相不锈钢的牌号和化学成分、双相不锈钢5种冶金工艺、太钢双相不锈钢的生产、高氮双相不锈钢的形变热处理以及双相不锈钢的研究和发展趋势。 相似文献
12.
Fawzy H. Samuel 《Metallurgical and Materials Transactions A》1984,15(10):1807-1817
The present study was carried out on four steels containing 0.1 pct C-1.5 pct Mn-0.003 pct B* in common, with additions of 1 pct Cr, 0.5 pct Mo, 0.25 pct Mo + 1 pct Cr, 0.2 pct Ti + 1 pct Cr. They were designated, accordingly, as Cr, Mo, Mo-Cr, and Cr-Ti steels. All the steels exhibited a complete lath martensite microstructure with thin interlaths of retained austenite (≈0.05 pct) in the quenched condition. The normalized microstructures, granular bainite, contained massive areas of ferrite and granules of bainite laths. Both microconstituents contained a fine dispersion of cementite particles (size ≈50 Å) together with high dislocation densities. A mechanism explaining their for-mation has been given. The Cr steel, due to its low hardenability, showed in addition polygonal ferrite in the neighborhood of the so-called M-A constituent (twinned martensite and/or austenite). The annealed microstructure (using a cooling rate of 0.033 °C s?1) of the Cr steel consisted of coarse ferrite-pearlite. Addition of 0.2 pct Ti to the Cr steel markedly refined the structure, whereas an addition of 0.25 pct Mo altered the microstructure to ferrite-lower bainite. In the 0.5 pct Mo steel, polygonal ferrite was found to be completely missing. The mechanical properties of the four steels after quenching, normalizing, and annealing were investigatedvia hardness and tensile test mea-surements. An empirical equation, relating the ultimate tensile strength to the steel composition, for steels that had granular bainite microstructures in the normalized condition, was proposed. The fracture surfaces exhibited cleavage and variable-size dimples depending on the microstructure and steel composition. 相似文献
13.
Xiaoping Ma Lijun Wang Sundaresa V. Subramanian Chunming Liu 《Metallurgical and Materials Transactions A》2012,43(12):4475-4486
The effect of Nb microalloying on microstructure, mechanical properties, and pitting corrosion properties of quenched and tempered 13?pct Cr-5?pct Ni-0.02?pct C martensitic stainless steels with different Mo and N contents was investigated. The microstructure, density, and dispersion of high-angle boundaries, nanoscale precipitates, and amount of retained austenite were characterized by using electron backscattered diffraction, transmission electron microscopy, and X-ray diffraction to correlate with properties. The results show that the combined effects of lowering nitrogen content in 13?pct Cr-5?pct Ni-1~2?pct Mo-0.02?pct C steels to 0.01?wt pct, and adding 0.1?pct Nb are to decrease the amount of Cr-rich precipitates, as Nb preferentially combines with residual carbon and nitrogen to form carbonitrides, suppressing the formation of Cr2N and Cr23C6. Austenite grain refinement can be achieved by Nb microalloying through proper heat treatment. If the nitrogen content is kept high, then Cr-rich precipitates would occur irrespective of microalloying addition. The NbN would also occur at high temperature, which will act as substrate for nucleation of coarse precipitates during subsequent tempering, impairing the toughness of the steel. It was shown that the addition of Nb to low interstitial super martensitic stainless steel retards the formation of reversed austenite and results in the formation of nanoscale precipitates (5 to 15?nm), which contribute to a significant increase in strength. More importantly, the pitting corrosion resistance was found to increase with Nb addition. This is attributed to suppression of Cr-rich precipitates, which can cause local depletion of Cr in the matrix and the initiation of pitting corrosion. 相似文献
14.
The classic series of duplex stainless steels shows very high corrosion resistance and can be used for very demanding applications. A new lean duplex steel, LDX 2101® (EN 1.4162, UNS S32101), has been developed with corrosion resistance on a par with standard austenitic grades. Application areas include: structural components, chemical industry, tanks and containers. The steel was designed to have equal amounts of ferrite and austenite in annealed condition and with an austenite that is stable against strain‐induced martensite. Thanks to its high nitrogen content, the steel has a fast austenite reformation when subjected to thermal cycling, e.g. welding. Unlike conventional duplex grades, the formation of intermetallic phase is very sluggish, although precipitation of nitrides and carbides has a certain impact on material properties after exposure in the temperature range 600 to 800°C. The precipitation behaviour after different isothermal treatments is described and its influence on different product properties is shown. A good agreement was found between impact toughness and corrosion resistance for a wide range of thermal treatments. 相似文献
15.
Fabrication of ultrahigh nitrogen austenitic steels by nitrogen gas absorption into solid solution 总被引:4,自引:0,他引:4
T. Tsuchiyama S. Takaki H. Ito K. Kataoka 《Metallurgical and Materials Transactions A》2003,34(11):2591-2599
For the purpose of fabricating ultrahigh nitrogen austenitic steels (>1 mass pct N), the phenomenon of nitrogen absorption
into solid solution was thermodynamically analyzed and applied to Fe-Cr-Mn system ternary alloy. During the annealing of the
steel in a nitrogen gas atmosphere of 0.1 MPa at 1473 K (nitrogen absorption treatment), the nitrogen content of the steel
was increased with the absorption of nitrogen gas from the material surface and then saturated when the system reached a state
of equilibrium. Effect of the steel composition on an equilibrium nitrogen content was formulated taking account of interactions
among Cr, Mn, and N atoms, and the condition for fabrication of ultrahigh nitrogen austenitic steels was clarified. The nitrogen
addition to ultrahigh content markedly increased proof stress and tensile stress of the austenitic steels without losing moderate
ductility. For example, Fe-24Cr-10Mn-1.43N (mass pct) alloy has 830 MPa in 0.2 pct proof stress, 2.2 GPa in true tensile stress,
and 75 pct in total elongation. As a result of tensile tests for various nitrogen-bearing austenitic steels, it was found
that the proof stress is increased in proportion to (atomic fraction of nitrogen)2/3. 相似文献
16.
A plain carbon and two microalloyed steels were tested under interrupted loading conditions. The base steel contained 0.06
pct C and 1.31 pct Mn, and the other alloys contained single additions of 0.29 pct Mo and 0.04 pct Nb. Double-hit compression
tests were performed on cylindrical specimens of the three steels at 820 °C, 780 °C, and 740 °C within the α + γ field. A’softening
curve was determined at each temperature by the offset method. In parallel, the progress of ferrite recrystallization was
followed on quenched specimens of the three steels by means of quantitative metallography. It was observed that, in the base
steel, a recrystallizes more slowly thany. The addition of Mo retards recrystallization and has a greater influence on γ than on α recrystallization. This effect is
in agreement with calculations based on the Cahn theory of solute drag. Niobium addition has an even greater effect on the
recrystallization of the two phases. In this steel, the recrystallization of ferrite was incomplete at the three intercritical
temperatures. Furthermore, the austenite remained completely unrecrystallized up to the maximum time involved in the experiments
(1 hour). The metallographic results indicate that the nucleation of recrystallization occurs heterogeneously in the microstructure,
the interface between ferrite and austenite being the preferred site for nucleation. 相似文献
17.
Metallographic studies have been conducted on a 0.024 pct C-16 pct Cr-1.5 pct Mo-5 pct Ni stainless steel to study the phase reactions associated with heat treatments and investigate the strengthening mechanisms of the steel. In the normalized condition, air cooled from 1010 °C, the microstructure consists of 20 pct ferrite and 80 pct martensite. Tempering in a temperature range between 500 and 600 °C results in a gradual transformation of martensite to a fine mixture of ferrite and austenite. At higher tempering temperatures, between 600 and 800 °C, progressively larger quantities of austenite form and are converted during cooling to proportionally increasing amounts of fresh martensite. The amount of retained austenite in the microstructure is reduced to zero at 800 °C, and the microstructure contains 65 pct re-formed martensite and 35 pct total ferrite. Chromium rich M23C6 carbides precipitate in the single tempered microstructures. The principal strengthening is produced by the presence of martensite in the microstructure. Additional strengthening is provided by a second tempering treatment at 400 °C due to the precipitation of ultrafine (Cr, Mo) (C,N) particles in the ferrite. 相似文献
18.
Hot-rolled and continuously cooled, medium-carbon microalloyed steels containing 0.2 or 0.4 pct C with vanadium (0.15 pct)
or vanadium (0.15 pct) plus niobium (0.04 pct) additions were investigated with light and transmission electron microscopy.
Energy dispersive spectroscopy in a scanning transmission electron microscope was conducted on precipitates of the 0.4 pct
C steel with vanadium and niobium additions. The vanadium steels contained fine interphase precipitates within ferrite, pearlite
nodules devoid of interphase precipitates, and fine ferritic transformation twins. The vanadium plus niobium steels contained
large Nb-rich precipitates, precipitates which formed in cellular arrays on deformed austenite substructure and contained
about equal amounts of niobium and vanadium, and V-rich interphase precipitates. Transformation twins in the ferrite and interphase
precipitates in the pearlitic ferrite were not observed in either of the steels containing both microalloying elements. Consistent
with the effect of higher C concentrations on driving the microalloying precipitation reactions, substructure precipitation
was much more frequently observed in the 0.4C-V-Nb steel than in the 0.2C-V-Nb steel, both in the ferritic and pearlitic regions
of the microstructure. Also, superposition of interphase and substructure precipitation was more frequently observed in the
high-C-V-Nb steel than in the similar low-C steel. 相似文献
19.
K. L. Chao H. Y. Liao J. J. Shyue S. S. Lian 《Metallurgical and Materials Transactions B》2014,45(2):381-391
The purpose of the current study is to develop austenitic nickel-free stainless steels with lower chromium content and higher manganese and nitrogen contents. In order to prevent nickel-induced skin allergy, cobalt, manganese, and nitrogen were used to substitute nickel in the designed steel. Our results demonstrated that manganese content greater than 14 wt pct results in a structure that is in full austenite phase. The manganese content appears to increase the solubility of nitrogen; however, a lower corrosion potential was found in steel with high manganese content. Molybdenum appears to be able to increase the pitting potential. The effects of Cr, Mn, Mo, and N on corrosion behavior of Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were evaluated with potentiodynamic tests and XPS surface analysis. The results reveal that anodic current and pits formation of the Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were smaller than those of lower manganese and nitrogen content stainless steel. 相似文献
20.
R. M. Davison 《Metallurgical and Materials Transactions B》1974,5(11):2287-2294
Because of its excellent corrosion resistance, low-interstitial 18 pct Cr-2 pct Mo ferritic stainless steel is being considered
for a wide range of applications, many of which involve the forming of sheet. The present investigation was undertaken to
examine the effects of rolling schedule on the formability of titanium-stabilized 18 pct Cr-2 pct Mo ferritic stainless steel
sheet. Formability and texture development were evaluated by utilizing 1) plastic strain ratios and work-hardening exponents
derived from tensile tests; 2) Swift and Olsen cup tests; and 3) X-ray pole figure analysis. Increasing the degree of cold
reduction from 70 pct to 92 pct prior to the final recrystallization anneal led to substantial increases in deep drawability
through changes in the recrystallization texture. Schedules of two-step cold rolling with an intervening recrystallization
anneal, leading to increased total cold reduction, produced significantly higher plastic strain ratios than those produced
by the one-step schedules. The crystallographic textures of the sheets were determined and correlated with the observedr values.
This paper is based on a presentation made at a symposium on “New Developments in Ferritic and Duplex Stainless Steels,” held
at the Fall Meeting in Cleveland, Ohio, on October 19, 1972, under the sponsorship of the Corrosion Resistant Metals Committee
on TMS-IMD and the Corrosion and Oxidation Activity of the ASM. 相似文献